Over 80 people are currently infected with mumps in Norway, well over the previous record set 15 years ago, Science Nordic reported this week.

According to Margrethe Greve-Isdahl, the chief physician at the Department of Vaccines for the Norwegian Institute of Public Health (NIPH), the normal annual figures are between eight and 35 people so the current number represents a major outbreak in Norway.

The recent outbreak of mumps reportedly stems from international students in Trondheim who were unsure if they had been vaccinated against the virus, Greve-Isdahl said. The NIPH suspects that the infection may have been spread at a student cultural festival in October, where the infected students from Trondheim came into contact with students from across Norway.

Three infection cases in Oslo and four in Bergen are all connected to the student community and the number infected in Bergen is most likely higher, according to officials.

The University of Bergen is taking steps to inform students about mumps by urging students to take extra precautions to prevent its spread.

The Norwegian-born students affected by the virus were in the age bracket to have received the MMR (measles, mumps and rubella) vaccination that was introduced in 1983, and those who contracted the contagious disease report that they were indeed vaccinated.

Greve-Isdahl explained to Science Nordic that “the mumps component of the MMR vaccine is the weakest one in the vaccine, and its effect can diminish over time, at least in some people.”

NIPH is recommending a second dose of the mumps vaccine primarily for individuals “who are missing one or both vaccine doses,” Greve-Isdahl said.

A recent press release from the municipality of Bergen is encouraging anyone who has been in close contact with a person infected with mumps to get a booster dose of the MMR-vaccine, regardless of their vaccination history.

Although the mumps virus can cause fever, headache, fatigue and swollen glands, Greve-Isdahl stressed that it is not in same dangerous league as the measles or rubella.

“We included mumps in the MMR vaccine because we want to limit the disease for the sake of boys. Boys who become infected after puberty may have complications with inflammation of the testicles, which can impair their ability to have children. These fertility problems may go away over time, so sterility is rarely long-term,” she told Science Nordic.